Skull shape and its implication for animal welfare

Syringomyelia (SM) is a painful condition in dogs that is more common in toy breeds like the Chihuahua and the Cavalier King Charles Spaniel. It involves the formation of fluid-filled cavities, known as syrinxes, in the spinal cord. In these toy breeds, SM is usually secondary to a specific malformation of the skull called Chiari-like Malformation, CM for short.

New research conducted at the University of Bristol’s School of Veterinary Sciences has identified two significant risk factors associated with these painful neurological conditions.

Identifying a head shape in dogs that is associated with these diseases would allow for selection away from these conditions and could be used to further breeding guidelines. Dogs were measured in several countries using a standardised “bony landmark” measuring system and photo analysis by trained researchers.

The researchers found two significant risk factors associated with CM/SM in the skull shape of the Cavalier King Charles Spaniel. These were the extent of the broadness of the top of skull relative to its length, also known as brachycephaly, and the distribution of doming of the skull. The study suggests that brachycephaly, with resulting doming towards the front of the head, is associated with both conditions.

Thomas Mitchell, who was the undergraduate involved in the study, says “The study also provides guidance to breed clubs, breeders and judges that have a responsibility to avoid obvious conditions or exaggerations which would be harmful in any way to the health, welfare or soundness of the breed. It will also provide vets with verified advice to provide to breeders outside the show ring and to occasional hobbyists.”